[sdl_omap.git] / docs / html / sdlsemwait.html

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>SDL_SemWait</TITLE
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><H1
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>SDL_SemWait</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN8023"
></A
><H2
>Name</H2
>SDL_SemWait&nbsp;--&nbsp;Lock a semaphore and suspend the thread if the semaphore value is zero.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN8026"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN8027"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"
#include "SDL_thread.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_SemWait</B
></CODE
>(SDL_sem *sem);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8033"
></A
><H2
>Description</H2
><P
><TT
CLASS="FUNCTION"
>SDL_SemWait()</TT
> suspends the calling thread until either
the semaphore pointed to by <TT
CLASS="PARAMETER"
><I
>sem</I
></TT
> has a positive value,
the call is interrupted by a signal or error. If the call is successful it
will atomically decrement the semaphore value.</P
><P
>After <TT
CLASS="FUNCTION"
>SDL_SemWait()</TT
> is successful, the semaphore
can be released and its count atomically incremented by a successful call to
<A
HREF="sdlsempost.html"
>SDL_SemPost</A
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8041"
></A
><H2
>Return Value</H2
><P
>Returns <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> if successful or
<SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> if there was an error (leaving the semaphore unchanged).</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8046"
></A
><H2
>Examples</H2
><P
><PRE
CLASS="PROGRAMLISTING"
>if (SDL_SemWait(my_sem) == -1) {
        return WAIT_FAILED;
}

...

SDL_SemPost(my_sem);</PRE
></P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8050"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlcreatesemaphore.html"
><TT
CLASS="FUNCTION"
>SDL_CreateSemaphore</TT
></A
>,
<A
HREF="sdldestroysemaphore.html"
><TT
CLASS="FUNCTION"
>SDL_DestroySemaphore</TT
></A
>,
<A
HREF="sdlsemtrywait.html"
><TT
CLASS="FUNCTION"
>SDL_SemTryWait</TT
></A
>,
<A
HREF="sdlsemwaittimeout.html"
><TT
CLASS="FUNCTION"
>SDL_SemWaitTimeout</TT
></A
>,
<A
HREF="sdlsempost.html"
><TT
CLASS="FUNCTION"
>SDL_SemPost</TT
></A
>,
<A
HREF="sdlsemvalue.html"
><TT
CLASS="FUNCTION"
>SDL_SemValue</TT
></A
></P
></DIV
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>
Commit	Line	Data
e14743d1	1	<HTML
	2	><HEAD
	3	><TITLE
	4	>SDL_SemWait</TITLE
	5	><META
	6	NAME="GENERATOR"
	7	CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
	8	"><LINK
	9	REL="HOME"
	10	TITLE="SDL Library Documentation"
	11	HREF="index.html"><LINK
	12	REL="UP"
	13	TITLE="Multi-threaded Programming"
	14	HREF="thread.html"><LINK
	15	REL="PREVIOUS"
	16	TITLE="SDL_DestroySemaphore"
	17	HREF="sdldestroysemaphore.html"><LINK
	18	REL="NEXT"
	19	TITLE="SDL_SemTryWait"
	20	HREF="sdlsemtrywait.html"></HEAD
	21	><BODY
	22	CLASS="REFENTRY"
	23	BGCOLOR="#FFF8DC"
	24	TEXT="#000000"
	25	LINK="#0000ee"
	26	VLINK="#551a8b"
	27	ALINK="#ff0000"
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	29	CLASS="NAVHEADER"
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	31	SUMMARY="Header navigation table"
	32	WIDTH="100%"
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	34	CELLPADDING="0"
	35	CELLSPACING="0"
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	37	><TH
	38	COLSPAN="3"
	39	ALIGN="center"
	40	>SDL Library Documentation</TH
	41	></TR
	42	><TR
	43	><TD
	44	WIDTH="10%"
	45	ALIGN="left"
	46	VALIGN="bottom"
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	48	HREF="sdldestroysemaphore.html"
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	50	>Prev</A
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	53	WIDTH="80%"
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	59	ALIGN="right"
	60	VALIGN="bottom"
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	62	HREF="sdlsemtrywait.html"
	63	ACCESSKEY="N"
	64	>Next</A
65	></TD
66	></TR
67	></TABLE
68	><HR
69	ALIGN="LEFT"
70	WIDTH="100%"></DIV
71	><H1
72	><A
73	NAME="SDLSEMWAIT"
74	></A
75	>SDL_SemWait</H1
76	><DIV
77	CLASS="REFNAMEDIV"
78	><A
79	NAME="AEN8023"
80	></A
81	><H2
82	>Name</H2
83	>SDL_SemWait -- Lock a semaphore and suspend the thread if the semaphore value is zero.</DIV
84	><DIV
85	CLASS="REFSYNOPSISDIV"
86	><A
87	NAME="AEN8026"
88	></A
89	><H2
90	>Synopsis</H2
91	><DIV
92	CLASS="FUNCSYNOPSIS"
93	><A
94	NAME="AEN8027"
95	></A
96	><P
97	></P
98	><PRE
99	CLASS="FUNCSYNOPSISINFO"
100	>#include "SDL.h"
101	#include "SDL_thread.h"</PRE
102	><P
103	><CODE
104	><CODE
105	CLASS="FUNCDEF"
106	>int <B
107	CLASS="FSFUNC"
108	>SDL_SemWait</B
109	></CODE
110	>(SDL_sem *sem);</CODE
111	></P
112	><P
113	></P
114	></DIV
115	></DIV
116	><DIV
117	CLASS="REFSECT1"
118	><A
119	NAME="AEN8033"
120	></A
121	><H2
122	>Description</H2
123	><P
124	><TT
125	CLASS="FUNCTION"
126	>SDL_SemWait()</TT
127	> suspends the calling thread until either
128	the semaphore pointed to by <TT
129	CLASS="PARAMETER"
130	><I
131	>sem</I
132	></TT
133	> has a positive value,
134	the call is interrupted by a signal or error. If the call is successful it
135	will atomically decrement the semaphore value.</P
136	><P
137	>After <TT
138	CLASS="FUNCTION"
139	>SDL_SemWait()</TT
140	> is successful, the semaphore
141	can be released and its count atomically incremented by a successful call to
142	<A
143	HREF="sdlsempost.html"
144	>SDL_SemPost</A
145	>.</P
146	></DIV
147	><DIV
148	CLASS="REFSECT1"
149	><A
150	NAME="AEN8041"
151	></A
152	><H2
153	>Return Value</H2
154	><P
155	>Returns <SPAN
156	CLASS="RETURNVALUE"
157	>0</SPAN
158	> if successful or
159	<SPAN
160	CLASS="RETURNVALUE"
161	>-1</SPAN
162	> if there was an error (leaving the semaphore unchanged).</P
163	></DIV
164	><DIV
165	CLASS="REFSECT1"
166	><A
167	NAME="AEN8046"
168	></A
169	><H2
170	>Examples</H2
171	><P
172	><PRE
173	CLASS="PROGRAMLISTING"
174	>if (SDL_SemWait(my_sem) == -1) {
175	return WAIT_FAILED;
176	}
177
178	...
179
180	SDL_SemPost(my_sem);</PRE
181	></P
182	></DIV
183	><DIV
184	CLASS="REFSECT1"
185	><A
186	NAME="AEN8050"
187	></A
188	><H2
189	>See Also</H2
190	><P
191	><A
192	HREF="sdlcreatesemaphore.html"
193	><TT
194	CLASS="FUNCTION"
195	>SDL_CreateSemaphore</TT
196	></A
197	>,
198	<A
199	HREF="sdldestroysemaphore.html"
200	><TT
201	CLASS="FUNCTION"
202	>SDL_DestroySemaphore</TT
203	></A
204	>,
205	<A
206	HREF="sdlsemtrywait.html"
207	><TT
208	CLASS="FUNCTION"
209	>SDL_SemTryWait</TT
210	></A
211	>,
212	<A
213	HREF="sdlsemwaittimeout.html"
214	><TT
215	CLASS="FUNCTION"
216	>SDL_SemWaitTimeout</TT
217	></A
218	>,
219	<A
220	HREF="sdlsempost.html"
221	><TT
222	CLASS="FUNCTION"
223	>SDL_SemPost</TT
224	></A
225	>,
226	<A
227	HREF="sdlsemvalue.html"
228	><TT
229	CLASS="FUNCTION"
230	>SDL_SemValue</TT
231	></A
232	></P
233	></DIV
234	><DIV
235	CLASS="NAVFOOTER"
236	><HR
237	ALIGN="LEFT"
238	WIDTH="100%"><TABLE
239	SUMMARY="Footer navigation table"
240	WIDTH="100%"
241	BORDER="0"
242	CELLPADDING="0"
243	CELLSPACING="0"
244	><TR
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246	WIDTH="33%"
247	ALIGN="left"
248	VALIGN="top"
249	><A
250	HREF="sdldestroysemaphore.html"
251	ACCESSKEY="P"
252	>Prev</A
253	></TD
254	><TD
255	WIDTH="34%"
256	ALIGN="center"
257	VALIGN="top"
258	><A
259	HREF="index.html"
260	ACCESSKEY="H"
261	>Home</A
262	></TD
263	><TD
264	WIDTH="33%"
265	ALIGN="right"
266	VALIGN="top"
267	><A
268	HREF="sdlsemtrywait.html"
269	ACCESSKEY="N"
270	>Next</A
271	></TD
272	></TR
273	><TR
274	><TD
275	WIDTH="33%"
276	ALIGN="left"
277	VALIGN="top"
278	>SDL_DestroySemaphore</TD
279	><TD
280	WIDTH="34%"
281	ALIGN="center"
282	VALIGN="top"
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284	HREF="thread.html"
285	ACCESSKEY="U"
286	>Up</A
287	></TD
288	><TD
289	WIDTH="33%"
290	ALIGN="right"
291	VALIGN="top"
292	>SDL_SemTryWait</TD
293	></TR
294	></TABLE
295	></DIV
296	></BODY
297	></HTML
298	>